In xerographic corona devices scorotron wires are employed to generate the electrostatic charges on a photoreceptor belt for developing an image thereon. Such devices have had filter material arranged in an air flow path over the scorotron wires to filter out effluents generated during the charging step of the copying process. As the photoreceptor belt is moved past the corona device, the scorotron wires are activated to impart the electrostatic charge on the belt. Activation of the scorotron wires develop undesirable gases within the corona cavity, including ozone and nitric oxide(s) NO, NO.sub.2 which should be filtered out (and or decomposed) before air is ejected into the surrounding atmosphere. In present corona devices, filters are arranged downstream of the corona cavity to filter out these unwanted effluents.
The problem with the system described above is the effect of gases and chemical compounds formed on the scorotron wires themselves, and ultimately the life of the corona device and photoreceptor belts. Premature failure of xerographic CRUs has been attributed to contamination deposit build up and growth on the corona devices. The discharged product such as ozone and nitric oxide(s) NO.sub.x (NO, NO.sub.2 . . .) may accumulate in the process and react with the environment to adversely affect the latent image on the photoreceptor belt. For example, silicon oil vapor and ammonia, which are known to be the primary contributors to SIO.sub.2 and ammonia nitrate dentrite and scale growth on the wires, can result in non-uniform charging, resulting in a flaming pattern on copies. This deposit on the wires and other effects of the unfiltered O.sub.3 and NO.sub.x gases in this environment can adversely affect the life of the corotron unit and photoreceptor. Charged ion species that are formed in the corona will also build up concentration and adversely affect the latent electrostatic image resulting in a loss in contrast.